This invention relates to a method for tagging macro-organisms and to an apparatus used in the performance of that method. More particularly, this invention relates to a method for tagging members of a large homogenous group of macro-organisms so that each macro-organism is assigned to a respective one of a plurality of statisically equivalent subgroups.
U.S. Pat. Nos. 3,128,744 and 3,313,301 to Jefferts et al. describe a method for investigating the migration and related physiological characteristics of macro-organisms existing individually or in groups. In those patents, a procedure is set forth wherein fish are tagged internally with small magnetically detectable particles carrying coded identification and information marks and released in their normal environment. The tagged organisms are subsequently recovered by passing a mass of captured organisms through a deflector gate mechanism operated under the control of a magnetic detector device.
Pursuant to the teachings of U.S. Pat. No. 3,545,405 to Jefferts, an identifying tag usable in the above-described method comprises a small metallic body of cylindrical shape cut from a continuous length of wire. The surface of the identifying tag contains along the circumference thereof binary coded information in the form of a plurality of minute indentations arranged in a predetermined pattern.
U.S. Pat. No. 3,820,545 to Jefferts discloses a method and apparatus for implanting identifying tags of the above-described type into macro-organisms so that movement of the macro-organisms from one habitat to another may be studied. In accordance with the disclosed method, the supply of wire is incrementally advanced along a substantially straight path through a cutting and implanting device which severs from the length of wire a short segment suitable for implantation. The implanting portion of the device includes a reciprocating hypodermic needle through which the cut wire segment is advanced by the supply of wire and implanted in the macroorganism.
In accordance with conventional tagging techniques, identifying tags of the kind described in U.S. Pat. No. 3,545,405 are "batch-coded," i.e., produced in groups ranging in size from 500 tags to 500,000 tags, with all tags in a respective group carrying the same identifying number or code. A current data format uses four words of binary data on the surface of the wire, each such word having seven binary digits spaced from one another longitudinally along the length of the wire. The separate words are circumferentially spaced from one another. One of the four words, referred to as the "master word," serves only to provide an indicator for the starting point and direction of reading for the remaining three words. Each of those remaining three words is commonly organized as six binary digits and one error check binary digit (parity bit).
Coded wire tags are manufactured and sold in wire form. Identification codes each somewhat shorter than the eventual tags are marked one after another down the length of the wire. The cutting and implanting device severs one tag from the end of the spool of wire during each machine cycle and each such severed tag is longer than one identification code. The usual tag is approximately 1.2 identification code groups in length. In batch coding, the extra length assures ease of reading of the tags even if the cutting operation distorts significant amounts of the tag ends. The reader simply begins at the starting point indicated by the master word, reads to the end of the tag in the direction indicated, then moves to the opposite end of the tag, and continues reading. This method of preparing and subsequently reading batch-coded tags is possible because all the tags are identical: the two ends of each tag carry fragments of the same identification code.
Many circumstances exist where random or pseudo-random assignment of an individual to one of a few statistically equivalent subgroups, as well as to the primary group is desired. For example, it may be desired to tag 100,000 fish with nominally identical tags, each fish being additionally assigned to one of five statistically equivalent subgroups.
A solution to this problem is to provide an additional subgroup number on the tags in the usual lengthwise fashion. However, if those tags are cut so that the data fields begin more or less in the middle of the tags, the subgroup identification codes associated with some tags are ambiguous inasmuch as the ends of each such tag are marked with parts different codes. The essence of the problem is that when more than one digit changes between adjacent tags, seriously ambiguous results may appear in the cutting and reading operations.
An object of the present invention is to provide a method of the above-described type for tagging members of a large homogenous group of macro-organisms so that each macro-organism is assigned to a respective one of a plurality of statistically equivalent subgroups without the afore-mentioned ambiguity in the cutting and reading operations.
Another, concomitant, object of the present invention is to provide an improved method of coding identification tags to facilitate the tagging of members of statistically equivalent subgroups of a primary group of macro-organisms.
Another, more particular, object of the present invention is to provide for use in an improved method of tagging, a wire marked with a succession of identification codes each having a word identifying a respective subgroup.